Activated Gαq family members induce Rho GTPase activation and Rho-dependent actin filament assembly

Rho GTPase is required for actin filament assembly and serum response element (SRE)-dependent gene transcription. Certain G protein-coupled receptors (GPCRs) induce Rho-dependent responses, but the intermediary signaling steps are poorly understood. The heterotrimeric Galpha12 family can induce Rho-dependent responses. In contrast, there are conflicting reports on the role of the Gaq family in Rho signaling. We report that expression of activated Gaq members, or activation of endogenous Galphaq via GPCR stimulation, induces SIZE reporter activation via Rho, and increased GTP-Rho levels. Moreover, microinjection of activated Gaq in fibroblasts induces actin stress fiber formation via Rho. Galphaq functionally cooperates with Lbc Rho guanine nucleotide exchange factor. Overall, these findings indicate that Galphaq family signals are sufficient to induce Rho-dependent cellular responses. (C) 2002 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.